Recent advances in antiviral activities and potential mechanisms of sulfated polysaccharides

Structural relationship of regioselectively-sulfonated botryosphaeran derivatives on activity against herpes simplex virus type 1

The bioactivities of sulfonated polysaccharides are frequently related to their substitution pattern. In this study, the regioselective sulfonation of an exocellular fungal (1→3)(1→6)-β-D-glucan (botryosphaeran) was performed by two different methods: mild sulfonation (MS) and via pivaloyl ester (PS), in order to study the influence of the sulfonation pattern on the antiviral activity of the respective derivatives. Two sulfonated derivatives with substitution degrees of 0.82 (MS) and 0.49 (PS) were obtained, with substitution patterns at positions C-6, and C-2/C-4 of the glucose units, respectively. All derivatives were chemically characterized and evaluated for antiviral activity against Herpes simplex virus type 1 (HSV-1) KOS strain, and dengue type 2 (DENV-2). The sample sulfonated at positions C-6 (MS) showed a remarkable antiviral effect on HSV-1 (IC50 of 5.38 μg mL1), while PS remained inactive. The investigation of the mode of action of sample MS pointed to the inhibition of HSV-1 adsorption to the host cells. Both samples were inactive towards the dengue virus strain. This study demonstrated that the presence of sulfate groups at the C-6 positions of botryosphaeran is the preferred substitution pattern that enables the antiviral activity towards HSV-1.

Microwave-assisted synthesis of highly sulfated mannuronate glycans as potential inhibitors against SARS-CoV-2

Algae-based marine carbohydrate drugs are typically decorated with negative ion groups such as carboxylate and sulfate groups. However, the precise synthesis of highly sulfated alginates is challenging, thus impeding their structure-activity relationship studies. Herein we achieve a microwave-assisted synthesis of a range of highly sulfated mannuronate glycans with up to 17 sulfation sites by overcoming the incomplete sulfation due to the electrostatic repulsion of crowded polyanionic groups. Although the partially sulfated tetrasaccharide had the highest affinity for the receptor binding domain (RBD) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant, the fully sulfated octasaccharide showed the most potent interference with the binding of the RBD to angiotensin-converting enzyme 2 (ACE2) and Vero E6 cells, indicating that the sulfated oligosaccharides might inhibit the RBD binding to ACE2 in a length-dependent manner.

Natural polysaccharides and their derivatives targeting the tumor microenvironment: A review

Polysaccharides have gained attention as valuable supplements and natural medicinal resources, particularly for their anti-tumor properties. Their low toxicity and potent anti-tumor effects make them promising candidates for cancer prevention and treatment. The tumor microenvironment is crucial in tumor development and offers potential avenues for novel cancer therapies. Research indicates that polysaccharides can positively influence the tumor microenvironment. However, the structural complexity of most anti-tumor polysaccharides, often heteropolysaccharides, poses challenges for structural analysis. To enhance their pharmacological activity, researchers have modified the structure and properties of natural polysaccharides based on structure-activity relationships, and they have discovered that many polysaccharides exhibit significantly enhanced anti-tumor activity after chemical modification. This article reviews recent strategies for targeting the tumor microenvironment with polysaccharides and briefly discusses the structure-activity relationships of anti-tumor polysaccharides. It also summarises the main chemical modification methods of polysaccharides and discusses the impact of chemical modifications on the anti-tumor activity of polysaccharides. The review aims to lay a theoretical foundation for the development of anti-tumor polysaccharides and their derivatives.

Pharmacokinetics, tissue distribution, and subacute toxicity of oral carrageenan in mice

Carrageenan (CGN) is a typical sulfated polysaccharide widely applied in the food and pharmaceutical industries. Its in vivo behavior plays vital roles in understanding structural and biological functional relationships. The lack of UV chromophores in highly sulfated polysaccharides presents a challenge for their in vivo behavior studies. Therefore, this study aimed to develop a fast and effective quantitative fluorescence method for investigating the pharmacokinetics and tissue distribution of CGN. Fluorescence isothiocyanate labeling of CGN (FCGN) and microplate reader-based measurements were developed and validated to study its pharmacokinetics. These results showed that the FCGN concentration peaked at 3 h, the mean residence time was 36.6 h, and the clearance rate was 0.1 L/h/kg. Most of the FCGN was excreted in the feces, while 9.2 % was excreted in the urine, suggesting absorption and metabolism. The pharmacokinetic parameters indicated that the FCGN was absorbed quickly, eliminated slowly, and could remain in the body for a sustained profile. Moreover, ex vivo imaging and quantification of FCGN in tissues revealed that FCGN accumulated in the liver and kidney. Furthermore, oral administration of CGN or KOs for 14 days led to changes in liver and kidney indices. Histological analysis of significant organs revealed hepatocyte necrosis in the liver, renal tubular vacuolization in the kidney, and incomplete colonic epithelial cells. The KOs had a more significant effect on inflammatory cell infiltration than did CGNs. These in vivo findings laid the foundation for the study and application of CGN in food and pharmaceutical applications.

Extraction, purification, structural features, modifications, bioactivities, structure-activity relationships, and applications of polysaccharides from garlic: A review

Garlic is a common vegetable and spice in people's daily diets, in which garlic polysaccharide (GP) is one of the most important active components with a variety of benefits, such as antioxidant, immune-enhancing, anti-inflammatory, liver-protective and bowel-regulating properties. >20 types of GPs, mainly crude polysaccharides, have been identified. However, the exact chemical composition of GPs or the mechanism underlying their pharmacological activity is still not fully understood. The extraction and purification methods of GPs are compared in this review while providing detailed information on their structural features, identification methods, major biological activities, mechanisms of actions, structural modifications, structure-activity relationships as well as potential applications. Finally, the limitations of GP research and future issues that need to be addressed are discussed in this review. GPs are widely recognized as substances with great potential in the pharmaceutical and food industries. Therefore, this review aims to provide a comprehensive summary of the latest research progresses in the field of GPs, together with scientific insights and a theoretical support for the development of GPs in research and industrialization.

Synthesis, molecular docking analysis, molecular dynamic simulation, ADMET, DFT, and drug likeness studies: Novel Indeno[1,2-b]pyrrol-4(1H)-one as SARS-CoV-2 main protease inhibitors

BACKGROUND

The COVID-19 pandemic began in 2019 as a result of the advent of a novel coronavirus, SARS-CoV-2. At present, there are a limited number of approved antiviral agents for the treatment of COVID-19. Remdesivir, Molnupiravir, and Paxlovid have been approved by the FDA to treat COVID-19 infections. Research has shown that the main protease enzyme (Mpro) of SARS-CoV-2 plays a crucial role in the enzymatic processing of viral polyproteins. This makes Mpro an interesting therapeutic target for combating infections caused by emerging coronaviruses.

METHODS

The pharmacological effects of pyrroles and their derivatives have a wide range of applications. In our study, we focused on synthesizing nine novel derivatives of 2-arylamino-dihydro-indeno[1,2-b] pyrrol-4(1H)-one, with a particular emphasis on their antiviral properties. Using in silico studies involving molecular docking and DFT analyses in the gas phase using the B3LYP/6-31++G(d,p) basis set, we studied these compounds with respect to their interactions with the Mpro of SARS-CoV-2. The results of the docking analysis revealed that the synthesized compounds exhibited favorable inhibitory effects. Notably, compound 5f demonstrated the highest effectiveness against the target protein. Furthermore, the pharmacokinetic and drug-like properties of the synthesized derivatives of 2-arylamino-dihydroindeno[1,2-b] pyrrol-4(1H)-one indicated their potential as promising candidates for further development as inhibitors targeting SARS-CoV-2. However, it is imperative to determine the in vitro efficacy of these compounds through comprehensive biochemical and structural analyses.

Investigating the cryoprotective efficacy of fructans in mammalian cell systems via a structure-functional perspective

Fructans have long been known with their role in protecting organisms against various stress factors due to their ability to induce controlled dehydration and support membrane stability. Considering the vital importance of such features in cryo-technologies, this study aimed to explore the cryoprotective efficacy of fructans in mammalian cell systems where structurally different fructan polymers were examined on in vitro cell models derived from organs such as the liver, frequently used in transplantation, osteoblast, and cord cells, commonly employed in cell banking, as well as human seminal fluids that are of vital importance in assisted reproductive technology. To gain insights into the fructan/membrane interplay, structural differences were linked to rheological properties as well as to lipid membrane interactions where both fluorescein leakage from unilamellar liposomes and membrane integrity of osteoblast cells were monitored. High survival rates obtained with human endothelial, osteoblast and liver cells for up to two months clearly showed that fructans could be considered as effective non-permeating cryoprotectants, especially for extended periods of cryopreservation. In trials with human seminal fluid, short chained levan in combination with human serum albumin and glycerol proved very effective in preserving semen samples across multiple patients without any morphological abnormalities.

Sulfated polysaccharides of Laetiporus sulphureus fruiting bodies exhibit anti-breast cancer activity through cell cycle arrest, apoptosis induction, and inhibiting cell migration

ETHNOPHARMACOLOGICAL RELEVANCE

Laetiporus sulphureus has long been used as an edible and medicinal mushroom in Asia, America, and Europe. Its fruiting bodies are widely used in folk medicine for treating cancer, gastric diseases, cough, and rheumatism. Polysaccharides are an important bioactive component of mushrooms. In nature, sulfated polysaccharides have never been reported in mushrooms. Furthermore, there is no information on differences in physicochemical properties and anti-breast cancer activities between polysaccharides (PS) and sulfated polysaccharides (SPS) of L. sulphureus.

AIM OF THE STUDY

This study aimed to investigate the physicochemical properties of PS and SPS isolated from fruiting bodies of L. sulphureus and examine their anti-proliferative effects and mechanism(s) of action on MDA-MB-231 breast cancer cells.

METHODS

Polysaccharides (PS) were isolated using hot water and ethanol precipitation methods. Sulfated polysaccharides (SPS) were isolated by the papain-assisted hydrolysis method. Physicochemical properties comprising sugar, protein, uronic acid, and sulfate contents, and molecular weight, monosaccharide composition, and structural conformation were analyzed on PS and SPS. In the anti-cancer study, a triple-negative breast cancer cell line (MDA-MB-231) and a normal human mammary epithelial cell line (H184B5F5/M10) were used to evaluate the anti-proliferative activity of PS and SPS, and their mechanism(s) of action.

RESULTS

The results showed that SPS, which had higher sulfate and protein contents and diversified monosaccharide composition, exhibited more potent anti-proliferative activity against MDA-MB-231 cells than PS. Furthermore, it had a selective cytotoxic effect on breast cancer cells but not the normal cells. SPS induced cell cycle arrest at G0/G1 phase via down-regulating CDK4 and cyclin D1 and up-regulating p21 protein expression. Breast cancer cell apoptosis was not observed until 72 h after SPS treatment. In addition, SPS also markedly inhibited breast cancer cell migration.

CONCLUSION

This study demonstrates that SPS exhibited selective cytotoxicity and was more potent than PS in inhibiting MDA-MB-231 cell proliferation. The contents of sulfate and protein, and monosaccharide composition could be the main factors affecting the anti-breast cancer activity of L. sulphureus SPS.

The efficient capture of polysaccharides in Tetradesmus obliquus of indole-3-acetic acid coupling sludge extraction

Polysaccharide is an important biomass of algae. The sludge extract is rich in organic substances, which can be used by algae for biomass growth and high-value biomass synthesis, but its organic toxicity has an inhibitory effect on algae. To overcome inhibition and improve polysaccharide enrichment, Tetradesmus obliquus was cultured with sludge extract with different indole-3-acetic acid (IAA) concentrations. Within 30 days of the culture cycle, T. obliquus showed in good condition at the IAA dosage content of 10-6 M, the maximum cell density and dry weight were respectively (106.78 ± 2.20) × 106 cell/mL and 2.941 ± 0.067 g/L while the contents of chlorophyll-a, chlorophyll-b, and carotenoid were 1.79, 1.91 and 2.80 times that of the blank group, respectively. The highest polysaccharide accumulation was obtained under this culture condition, reaching 533.15 ± 21.11 mg/L on the 30th day, which was 2.49 times that in the blank group. By FT-IR and NMR analysis, it was found that the polysaccharides of T. obliquus were sulfated polysaccharide with glucose and rhamnose as the main monosaccharides. Proteomic showed that the up-regulation of A0A383WL26 and A0A383WLM8 enhanced the light trapping ability, and A0A383WMJ2 enhanced the accumulation of NADPH. The up-regulation of A0A383WHD5 and A0A383WAY6 indicated that IAA culture could repair the damage caused by sludge toxicity, thus promoting the accumulation of biomass. The above findings provided new insights into the mechanism of sludge toxicity removal of T. obliquus and the enhancement of the polysaccharide accumulation effect under different concentrations of IAA.

Chemically modified galactans of Grateloupia indica: From production to in vitro antiviral activity

Herpes simplex viruses (HSVs) have an affinity for heparan sulfate proteoglycans on cell surfaces, which is a determinant for virus entry. Herein, several sulfated galactans that mimic the active domain of the entry receptor were employed to prevent HSV infection. They were produced from Grateloupia indica using chlorosulfonic acid-pyridine (ClSO3H.Py)/N,N-dimethylformamide reagent (fraction G-402), SO3.Py/DMF reagent (G-403), or by aqueous extraction (G-401). These galactans contained varied molecular masses (33-55 kDa), and sulfate contents (12-20 %), and have different antiviral activities. Especially, the galactan (G-402) generated by using ClSO3H.Py/DMF, a novel reagent, exhibited the highest level of antiviral activity (EC50 = 0.36 μg/mL) compared to G-403 (EC50 = 15.6 μg/mL) and G-401 (EC50 = 17.9 μg/mL). This most active sulfated galactan possessed a linear chain containing β-(1 → 3)- and α-(1 → 4)-linked Galp units with sulfate group at the O-2/4/6 and O-2/3/6 positions, respectively. The HSV-1 and HSV-2 strains were specifically inhibited by this novel 33 ± 15 kDa galactan, which also blocked the virus from entering the host cell. These results highlight the significant potential of this sulfated galactan for antiviral research and drug development. Additionally, the reagent used for the effective conversion of galactan hydroxy groups to sulfate during extraction may also be useful for the chemical transformation of other natural products.

Research Progress of Polysaccharide-Gold Nanocomplexes in Drug Delivery

Clinical drug administration aims to deliver drugs efficiently and safely to target tissues, organs, and cells, with the objective of enabling their therapeutic effects. Currently, the main approach to enhance a drug's effectiveness is ensuring its efficient delivery to the intended site. Due to the fact that there are still various drawbacks of traditional drug delivery methods, such as high toxicity and side effects, insufficient drug specificity, poor targeting, and poor pharmacokinetic performance, nanocarriers have emerged as a promising alternative. Nanocarriers possess significant advantages in drug delivery due to their size tunability and surface modifiability. Moreover, nano-drug delivery systems have demonstrated strong potential in terms of prolonging drug circulation time, improving bioavailability, increasing drug retention at the tumor site, decreasing drug resistance, as well as reducing the undesirable side effects of anticancer drugs. Numerous studies have focused on utilizing polysaccharides as nanodelivery carriers, developing delivery systems based on polysaccharides, or exploiting polysaccharides as tumor-targeting ligands to enhance the precision of nanoparticle delivery. These types of investigations have become commonplace in the academic literature. This review aims to elucidate the preparation methods and principles of polysaccharide gold nanocarriers. It also provides an overview of the factors that affect the loading of polysaccharide gold nanocarriers with different kinds of drugs. Additionally, it outlines the strategies employed by polysaccharide gold nanocarriers to improve the delivery efficiency of various drugs. The objective is to provide a reference for further development of research on polysaccharide gold nanodelivery systems.

Prunella vulgaris polysaccharide inhibits herpes simplex virus infection by blocking TLR-mediated NF-κB activation

BACKGROUND

Prunella vulgaris polysaccharide extracted by hot water and 30% ethanol precipitation (PVE30) was reported to possess potent antiviral effects against herpes simplex virus (HSV) infection. However, its anti-HSV mechanism has not yet been fully elucidated.

PURPOSE

This study aimed to investigate the potential mechanisms of PVE30 against HSV infection.

METHODS

Antiviral activity was evaluated by a plaque reduction assay, and the EC50 value was calculated. Immunofluorescence staining and heparin bead pull-down assays confirmed the interactions between PVE30 and viral glycoproteins. Real-time PCR was conducted to determine the mRNA levels of viral genes, including UL54, UL29, UL27, UL44, and US6, and the proinflammatory cytokines IL-6 and TNF-α. The protein expression of viral proteins (ICP27, ICP8, gB, gC, and gD), the activity of the TLR-NF-κB signalling pathway, and necroptotic-associated proteins were evaluated by Western blotting. The proportion of necroptotic cells was determined by flow cytometric analysis.

RESULTS

The P. vulgaris polysaccharide PVE30 was shown to compete with heparan sulfate for interaction with HSV surface glycoprotein B and gC, thus strongly inhibiting HSV attachment to cells. In addition, PVE30 downregulated the expression of IE genes, which subsequently downregulated the expression of E and L viral gene products, and thus effectively restricted the yield of progeny virus. Further investigation confirmed that PVE30 inhibited TLR2 and TLR3 signalling, leading to the effective suppression of NF-κB activation and IL-6 and TNF-α expression levels, and blocked HSV-1-induced necroptosis by reducing HSV-1-induced phosphorylation of MLKL.

CONCLUSION

Our results demonstrate that the P. vulgaris polysaccharide PVE30 is a potent anti-HSV agent that blocks TLR-mediated NF-κB activation.

The Relationship between Preparation and Biological Activities of Animal-Derived Polysaccharides: A Comprehensive Review

Polysaccharides are biomolecules found in microorganisms, plants, and animals that constitute living organisms. Glycosaminoglycans, unique acidic polysaccharides in animal connective tissue, are often combined with proteins in the form of covalent bonds due to their potent biological activity, low toxicity, and minimal side effects, which have the potential to be utilized as nutrition healthcare and dietary supplements. Existing studies have demonstrated that the bioactivity of polysaccharides is closely dependent on their structure and chain conformation. The characteristic functional groups and primary structure directly determine the strength of activity. However, the relationship between structure and function is still unclear, and the target and mechanism of action are not fully understood, resulting in limited clinical applications. As a result, the clinical applications of these polysaccharides are currently limited. This review provides a comprehensive summary of the extraction methods, structures, and biological activities of animal-derived polysaccharides that have been discovered so far. The aim is to promote developments in animal active polysaccharide science and provide theoretical support for exploring other unknown natural products.

Investigation of Bucillamine as anti-COVID-19 drug: DFT study, molecular docking, molecular dynamic simulation and ADMET analysis

The novel coronavirus disease-2019 (COVID-19), caused by SARS-CoV-2, is a global health pandemic beginning in early December 2019 in Wuhan, Hubei province, China. The effective drug target among coronaviruses is the SARS-CoV-2 main protease (Mpro), because of its crucial role in processing viral polyproteins translated from the viral RNA. In this study, the bioactivity of the selected thiol drug named Bucillamine (BUC) was evaluated as a potential drug for COVID-19 treatment by using computational modeling strategies. First, the molecular electrostatic potential density (ESP) calculation was performed to estimate the chemically active atoms of BUC. Additionally, BUC was docked to the Mpro (PDB: 6LU7) to evaluate the protein-ligand binding affinities. Besides, the estimated ESP results by density functional theory (DFT) were used to illustrate the molecular docking findings. Moreover, the frontier orbitals analysis was calculated to determine the charge transfer between the Mpro and BUC. Then, the stability of protein-ligand complex was subjected to the molecular dynamic simulations. Finally, an in silico study was performed to predict drug-likeness and absorption, distribution, metabolism, excretion and toxicity profiles (ADMET) of BUC. These results propose that BUC can be a potential drug candidate against the COVID-19 disease progression.Communicated by Ramaswamy H. Sarma.

Bio-Inspired Self-Healing, Shear-Thinning, and Adhesive Gallic Acid-Conjugated Chitosan/Carbon Black Composite Hydrogels as Suture Support Materials

The occurrence of leakage from anastomotic sites is a significant issue given its potential undesirable complications. The management of anastomotic leakage after gastrointestinal surgery is particularly crucial because it is directly associated with mortality and morbidity in patients. If adhesive materials could be used to support suturing in surgical procedures, many complications caused by leakage from the anastomosis sites could be prevented. In this study, we have developed self-healing, shear-thinning, tissue-adhesive, carbon-black-containing, gallic acid-conjugated chitosan (CB/Chi-gallol) hydrogels as sealing materials to be used with suturing. The addition of CB into Chi-gallol solution resulted in the formation of a crosslinked hydrogel with instantaneous solidification. In addition, these CB/Chi-gallol hydrogels showed enhancement of the elastic modulus (G') values with increased CB concentration. Furthermore, these hydrogels exhibited excellent self-healing, shear-thinning, and tissue-adhesive properties. Notably, the hydrogels successfully sealed the incision site with suturing, resulting in a significant increase in the bursting pressure. The proposed self-healing and adhesive hydrogels are potentially useful in versatile biomedical applications, particularly as suture support materials for surgical procedures.

Preparation, structures, and biological functions of rhamnan sulfate from green seaweed of the genus Monostroma: A review

Rhamnan sulfate, a rhamnose-rich sulfated polysaccharide, is present in the cell walls of green seaweed belonging to the genus Monostroma. This macromolecule demonstrates promising therapeutic properties, including anti-coagulant, thrombolytic, anti-viral, anti-obesity, and anti-inflammatory activities, which hold potential applications in food and medical industries. However, rhamnan sulfate has not garnered as much attention from researchers as other seaweed polysaccharides, including alginate, carrageenan, and fucoidan. This review discusses the extraction and purification techniques of rhamnan sulfate, delves into its chemical structures and related elucidation approaches, and provides an overview of its biological functions. Future research should focus on the structure-activity relationship of rhamnan sulfate and the industrial preparation of rhamnan sulfate with a specific homogeneous structure to facilitate its practical applications.

Ulvan and Ulva oligosaccharides: a systematic review of structure, preparation, biological activities and applications

Ulva is one of the main green algae causing green tide disasters. Ulvan is the primarily component polysaccharide of the cell wall of Ulva and its complex structure and monosaccharide composition resulted in various biological activities. However, the high-value and effective utilization of extracted ulvan have been obstructed by limitations ranging from large molecular weight and low solubility to poor bioavailability. Ulva oligosaccharide obtained by degrading ulvan can not only ideally retain the various biological activities of ulvan very well but also effectively solve the problems of low solubility and poor bioavailability. The preparation and biological activity studies of ulvan and Ulva oligosaccharides have become a hot spot in the field of marine biological resources development research. At present, the comprehensive reviews of ulvan and Ulva oligosaccharides are still scarce. What are overviewed in this paper are the chemical composition, structure, extraction, and purification of ulvan and Ulva oligosaccharides, where research progress on the biological activities of ulvan and Ulva oligosaccharides is summarized and prospected. A theoretical and practical basis has been provided for further research on ulvan and Ulva oligosaccharides, as well as the high-value development and effective utilization of marine algae resources.

Sulfated Polysaccharides from Seaweeds: A Promising Strategy for Combatting Viral Diseases-A Review

The limited availability of treatments for many infectious diseases highlights the need for new treatments, particularly for viral infections. Natural compounds from seaweed are attracting increasing attention for the treatment of various viral diseases, and thousands of novel compounds have been isolated for the development of pharmaceutical products. Seaweed is a rich source of natural bioactive compounds, including polysaccharides. The discovery of algal polysaccharides with antiviral activity has significantly increased in the past few decades. Furthermore, unique polysaccharides isolated from seaweeds, such as carrageenan, alginates, fucoidans, galactans, laminarians, and ulvans, have been shown to act against viral infections. The antiviral mechanisms of these agents are based on their inhibition of DNA or RNA synthesis, viral entry, and viral replication. In this article, we review and provide an inclusive description of the antiviral activities of algal polysaccharides. Additionally, we discuss the challenges and opportunities for developing polysaccharide-based antiviral therapies, including issues related to drug delivery and formulation. Finally, this review highlights the need for further research for fully understanding the potential of seaweed polysaccharides as a source of antiviral agents and for developing effective treatments for viral diseases.

Significance of culture period on the physiochemistry and anti-cancer potentials of polysaccharides from mycelia of Ganoderma lucidum

Ganoderma lucidum polysaccharides (GPS) have many functions. Polysaccharides are abundant in G. lucidum mycelia, but it is unclear whether the production and chemical characteristics of polysaccharides are related to the liquid cultural periods of mycelia. This study harvests G. lucidum mycelia at different cultural stages and isolates GPS and sulfated polysaccharides (GSPS) separately to determine an optimum cultural duration. After 42 and 49 days of mycelia are found to be the best times to harvest GPS and GSPS. Characteristic studies show that glucose and galactose are the main sugars in GPS and GSPS. The molecular weights of various GPS and GSPS are mainly distributed at >1000 kDa and from 101 to 1000 kDa. The sulfate content of GSPS at Day 49 is greater than that at Day 7. GPS and GSPS at 49 days exhibits a good anticancer effect but does not affect normal fibroblasts. GPS and GSPS that is isolated on day 49 inhibits lung cancer by suppressing epidermal growth factor receptor (EGFR) and transforming growth factor beta receptor (TGFβR)-mediated signaling networks. These results show that the mycelia of G. lucidum that are cultured for 49 days exhibit the best biological characteristics.

Structure, anti-SARS-CoV-2, and anticoagulant effects of two sulfated galactans from the red alga Botryocladia occidentalis

The structure of the sulfated galactan from the red alga Botryocladia occidentalis (BoSG) was originally proposed as a simple repeating disaccharide of alternating 4-linked α-galactopyranose (Galp) and 3-linked β-Galp units with variable sulfation pattern. Abundance was estimated only for the α-Galp units: one-third of 2,3-disulfation and one-third of 2-monosulfation. Here, we isolated again the same BoSG fractions from the anion-exchange chromatography, obtaining the same NMR profile of the first report. More careful NMR analysis led us to revise the structure. A more complex sulfation pattern was noted along with the occurrence of 4-linked α-3,6-anhydro-Galp (AnGalp) units. Interestingly, the more sulfated BoSG fraction showed slightly reduced in vitro anti-SARS-CoV-2 activities against both wild-type and delta variants, and significantly reduced anticoagulant activity. The BoSG fractions showed no cytotoxic effects. The reduction in both bioactivities is attributed to the presence of the AnGalp unit. Docking scores from computational simulations using BoSG disaccharide constructs on wild-type and delta S-proteins, and binding analysis through competitive SPR assays using blood (co)-factors (antithrombin, heparin cofactor II and thrombin) and four S-proteins (wild-type, delta, gamma, and omicron) strongly support the conclusion about the deleterious impact of the AnGalp unit.

Effects of Pine Pollen Polysaccharides and Sulfated Polysaccharides on Ulcerative Colitis and Gut Flora in Mice

Polysaccharides are important biological macromolecules in all organisms, and have recently been studied as therapeutic agents for ulcerative colitis (UC). However, the effects of Pinus yunnanensis pollen polysaccharides on ulcerative colitis remains unknown. In this study, dextran sodium sulfate (DSS) was used to induce the UC model to investigate the effects of Pinus yunnanensis pollen polysaccharides (PPM60) and sulfated polysaccharides (SPPM60) on UC. We evaluated the improvement of polysaccharides on UC by analyzing the levels of intestinal cytokines, serum metabolites and metabolic pathways, intestinal flora species diversity, and beneficial and harmful bacteria. The results show that purified PPM60 and its sulfated form SPPM60 effectively alleviated the disease progression of weight loss, colon shortening and intestinal injury in UC mice. On the intestinal immunity level, PPM60 and SPPM60 increased the levels of anti-inflammatory cytokines (IL-2, IL-10, and IL-13) and decreased the levels of proinflammatory cytokines (IL-1β, IL-6, and TNF-α). On the serum metabolism level, PPM60 and SPPM60 mainly regulated the abnormal serum metabolism of UC mice by regulating the energy-related and lipid-related metabolism pathways, respectively. On the intestinal flora level, PPM60 and SPPM60 reduced the abundance of harmful bacteria (such as Akkermansia and Aerococcus) and induced the abundance of beneficial bacteria (such as lactobacillus). In summary, this study is the first to evaluate the effects of PPM60 and SPPM60 on UC from the joint perspectives of intestinal immunity, serum metabolomics, and intestinal flora, which may provide an experimental basis for plant polysaccharides as an adjuvant clinical treatment of UC.

Antiviral and Antibacterial Sulfated Polysaccharide-Chitosan Nanocomposite Particles as a Drug Carrier

Drug delivery system (DDS) refers to the method of delivering drugs to the targeted sites with minimal risk. One popular strategy of DDS is using nanoparticles as a drug carrier, which are made from biocompatible and degradable polymers. Here, nanoparticles composed of Arthrospira-derived sulfated polysaccharide (AP) and chitosan were developed and expected to possess the capabilities of antiviral, antibacterial, and pH-sensitive properties. The composite nanoparticles, abbreviated as APC, were optimized for stability of morphology and size (~160 nm) in the physiological environment (pH = 7.4). Potent antibacterial (over 2 μg/mL) and antiviral (over 6.596 μg/mL) properties were verified in vitro. The pH-sensitive release behavior and release kinetics of drug-loaded APC nanoparticles were examined for various categories of drugs, including hydrophilic, hydrophobic, and protein drugs, under different pH values of the surroundings. Effects of APC nanoparticles were also evaluated in lung cancer cells and neural stem cells. The use of APC nanoparticles as a drug delivery system maintained the bioactivity of the drug to inhibit the proliferation of lung cancer cells (with ~40% reduction) and to relieve the growth inhibitory effect on neural stem cells. These findings indicate that the pH-sensitive and biocompatible composite nanoparticles of sulfated polysaccharide and chitosan well keep the antiviral and antibacterial properties and may serve as a promising multifunctional drug carrier for further biomedical applications.

Fucoidan-Derived Functional Oligosaccharides: Recent Developments, Preparation, and Potential Applications

Oligosaccharides derived from natural resources are attracting increasing attention as both food and nutraceutical products because of their beneficial health effects and lack of toxicity. During the past few decades, many studies have focused on the potential health benefits of fucoidan. Recently, new interest has emerged in fucoidan, partially hydrolysed into fuco-oligosaccharides (FOSs) or low-molecular weight fucoidan, owing to their superior solubility and biological activities compared with fucoidan. There is considerable interest in their development for use in the functional food, cosmetic, and pharmaceutical industries. Therefore, this review summarises and discusses the preparation of FOSs from fucoidan using mild acid hydrolysis, enzymatic depolymerisation, and radical degradation methods, and discusses the advantages and disadvantages of hydrolysis methods. Several purification steps performed to obtain FOSs (according to the latest reports) are also reviewed. Moreover, the biological activities of FOS that are beneficial to human health are summarised based on evidence from in vitro and in vivo studies, and the possible mechanisms for the prevention or treatment of various diseases are discussed.

In Vitro Anti-HIV-1 Activity of Chitosan Oligomers N-Conjugated with Asparagine and Glutamine

Chitosan oligomers (COS) are polysaccharides obtained by the hydrolyzation of chitosan. They are water-soluble, biodegradable, and have a wide range of beneficial properties for human health. Studies have shown that COS and its derivatives possess antitumor, antibacterial, antifungal, and antiviral activities. The goal of the current study was to investigate the anti-human immunodeficiency virus-1 (HIV-1) potential of amino acid-conjugated COS compared to COS itself. The HIV-1 inhibitory effects of asparagine-conjugated (COS-N) and glutamine-conjugated (COS-Q) COS were evaluated by their ability to protect C8166 CD4+ human T cell lines from HIV-1 infection and infection-mediated death. The results show that the presence of COS-N and COS-Q was able to prevent cells from HIV-1-induced lysis. Additionally, p24 viral protein production was observed to be suppressed in COS conjugate-treated cells compared to COS-treated and untreated groups. However, the protective effect of COS conjugates diminished by delayed treatment indicated an early stage inhibitory effect. COS-N and COS-Q did not show any inhibitory effect on the activities of HIV-1 reverse transcriptase and protease enzyme. The results suggest that COS-N and COS-Q possess an HIV-1 entry inhibition activity compared to COS and further studies to develop different peptide and amino acid conjugates containing N and Q amino acids might yield more effective compounds to battle HIV-1 infection.

Antiherpetic Activity of Carrageenan Complex with Echinochrome A and Its Liposomal Form

Herpes simplex virus (HSV) infections, the incidence of which is still widespread throughout the world, are actualizing the search and development of new, more effective antiherpetic drugs. The development of multifunctional drug delivery systems, including liposome-based ones, has become a relevant and attractive concept in nanotechnology. The ability of complexes of κ- and Σ-carrageenans (CRGs)-sulfated polysaccharides of red algae, with echinochrome A (Ech), as well as the liposomal form of the Σ-CRG/Ech complex-to inhibit different stages of HSV-1 infection in Vero cells was studied. By quantum chemical calculations, it was shown that CRG forms stable complexes with Ech. We have shown that complexes of κ-CRG/Ech and Σ-CRG/Ech exhibit highest virucidal activity with a selectivity index (SI) of 270 and 350, respectively, and inhibition of virus-cell interaction (SI of 83 and 32, respectively). The liposomal form of the Σ-CRG/Ech complex after virus adsorption and penetration to cells effectively reduced the HSV-1 plaque formation. The virus-inhibiting activity of the liposomal form of the Σ-CRG/Ech complex was three times higher than that of the Σ-CRG/Ech complex itself. Obtaining CRGs/Ech complexes and their liposomal forms can become the basis of a successful strategy for the development of promising antiherpetic drugs.

Prospects for the Use of Marine Sulfated Fucose-Rich Polysaccharides in Treatment and Prevention of COVID-19 and Post-COVID-19 Syndrome

Symptoms of the new coronavirus infection that appeared in 2019 (COVID-19) range from low fever and fatigue to acute pneumonia and multiple organ failure. The clinical picture of COVID-19 is heterogeneous and involves most physiological systems; therefore, drugs with a wide spectrum of mechanism of action are required. The choice of the treatment strategy for post-COVID-19 syndrome is still a challenge to be resolved. Polysaccharides with a high fucose content derived from seaweed and marine animals can form the basis for the subsequent development of promising agents for the treatment of COVID-19 and post-COVID-19 syndrome. This class of biopolymers is characterized by a variety of biological activities, including antiviral, antithrombotic, anticoagulant, hemo-stimulating, anti-inflammatory and immune-regulatory. Low molecular weight derivatives of these polysaccharides, as well as synthetic oligosaccharides with a sufficient amount and sulfation type may be considered as the most promising compounds due to their better bioavailability, which undoubtedly increases their therapeutic potential.

Research progress on the antiviral activities of natural products and their derivatives: Structure–activity relationships

Viruses spread rapidly and are well-adapted to changing environmental events. They can infect the human body readily and trigger fatal diseases. A limited number of drugs are available for specific viral diseases, which can lead to non-efficacy against viral variants and drug resistance, so drugs with broad-spectrum antiviral activity are lacking. In recent years, a steady stream of new viral diseases has emerged, which has prompted development of new antiviral drugs. Natural products could be employed to develop new antiviral drugs because of their innovative structures and broad antiviral activities. This review summarizes the progress of natural products in antiviral research and their bright performance in drug resistance issues over the past 2 decades. Moreover, it fully discusses the effect of different structural types of natural products on antiviral activity in terms of structure–activity relationships. This review could provide a foundation for the development of antiviral drugs.

Sulfonated (1 → 6)-β-d-Glucan (Lasiodiplodan): A Promising Candidate against the Acyclovir-Resistant Herpes Simplex Virus Type 1 (HSV-1) Strain

Herpes simplex virus type 1 (HSV-1) is a persistent human pathogen, and the emergence of strains resistant to Acyclovir (ACV, reference drug) shows the urgency to develop new treatments. We report the antiherpetic mechanism of the action of lasiodiplodan (LAS-N, (1 → 6)-β-d-glucan) and its sulfonated derivative (LAS-S3) in vitro and in vivo. LAS-S3 showed anti-HSV-1 action with high selectivity indices for HSV-1 KOS (88.1) and AR (189.2), sensitive and resistant to ACV, respectively. LAS-S3 inhibited >80% of HSV-1 infection in different treatment protocols (virucidal, adsorption inhibition, and post-adsorption effects), even at low doses, and showed a preventive effect and DNA and protein synthesis inhibition. The antiherpetic effect was confirmed in vivo by the cosmetic LAS-S3-CRÈME decreasing cutaneous lesions of HSV-1, including the AR strain. LAS-S3 possessed a broad-spectrum mechanism of action acting in the early and post-adsorption stages of HSV-1 infection, and LAS-S3-CRÈME is a potential antiherpetic candidate for patients infected by HSV-1-resistant strains.

Polysaccharide Based Implantable Drug Delivery: Development Strategies, Regulatory Requirements, and Future Perspectives

Implantable drug delivery systems advocate a wide array of potential benefits, including effective administration of drugs at lower concentrations and fewer side-effects whilst increasing patient compliance. Amongst several polymers used for fabricating implants, biopolymers such as polysaccharides are known for modulating drug delivery attributes as desired. The review describes the strategies employed for the development of polysaccharide-based implants. A comprehensive understanding of several polysaccharide polymers such as starch, cellulose, alginate, chitosan, pullulan, carrageenan, dextran, hyaluronic acid, agar, pectin, gellan gum is presented. Moreover, biomedical applications of these polysaccharide-based implantable devices along with the recent advancements carried out in the development of these systems have been mentioned. Implants for the oral cavity, nasal cavity, bone, ocular use, and antiviral therapy have been discussed in detail. The regulatory considerations with respect to implantable drug delivery has also been emphasized in the present work. This article aims to provide insights into the developmental strategies for polysaccharide-based implants.

Progress in Research of Chitosan Chemical Modification Technologies and Their Applications

Chitosan, which is derived from chitin, is the only known natural alkaline cationic polymer. Chitosan is a biological material that can significantly improve the living standard of the country. It has excellent properties such as good biodegradability, biocompatibility, and cell affinity, and has excellent biological activities such as antibacterial, antioxidant, and hemostasis. In recent years, the demand has increased significantly in many fields and has huge application potential. Due to the poor water solubility of chitosan, its wide application is limited. However, chemical modification of the chitosan matrix structure can improve its solubility and biological activity, thereby expanding its application range. The review covers the period from 1996 to 2022 and was elaborated by searching Google Scholar, PubMed, Elsevier, ACS publications, MDPI, Web of Science, Springer, and other databases. The various chemical modification methods of chitosan and its main activities and application research progress were reviewed. In general, the modification of chitosan and the application of its derivatives have had great progress, such as various reactions, optimization of conditions, new synthetic routes, and synthesis of various novel multifunctional chitosan derivatives. The chemical properties of modified chitosan are usually better than those of unmodified chitosan, so chitosan derivatives have been widely used and have more promising prospects. This paper aims to explore the latest progress in chitosan chemical modification technologies and analyze the application of chitosan and its derivatives in various fields, including pharmaceuticals and textiles, thus providing a basis for further development and utilization of chitosan.

Fucose-Rich Sulfated Polysaccharides from Two Vietnamese Sea Cucumbers Bohadschia argus and Holothuria (Theelothuria) spinifera: Structures and Anticoagulant Activity

Fucosylated chondroitin sulfates (FCSs) FCS-BA and FCS-HS, as well as fucan sulfates (FSs) FS-BA-AT and FS-HS-AT were isolated from the sea cucumbers Bohadschia argus and Holothuria (Theelothuria) spinifera, respectively. Purification of the polysaccharides was carried out by anion-exchange chromatography on DEAE-Sephacel column. Structural characterization of polysaccharides was performed in terms of monosaccharide and sulfate content, as well as using a series of non-destructive NMR spectroscopic methods. Both FCSs were shown to contain a chondroitin core [→3)-β-d-GalNAc-(1→4)-β-d-GlcA-(1→]_n bearing sulfated fucosyl branches at O-3 of every GlcA residue in the chain. These fucosyl residues were different in pattern of sulfation: FCS-BA contained Fuc2S4S, Fuc3S4S and Fuc4S at a ratio of 1:8:2, while FCS-HS contained these residues at a ratio of 2:2:1. Polysaccharides differed also in content of GalNAc4S6S and GalNAc4S units, the ratios being 14:1 for FCS-BA and 4:1 for FCS-HS. Both FCSs demonstrated significant anticoagulant activity in clotting time assay and potentiated inhibition of thrombin, but not of factor Xa. FS-BA-AT was shown to be a regular linear polymer of 4-linked α-L-fucopyranose 3-sulfate, the structure being confirmed by NMR spectra of desulfated polysaccharide. In spite of considerable sulfate content, FS-BA-AT was practically devoid of anticoagulant activity. FS-HS-AT cannot be purified completely from contamination of some FCS. Its structure was tentatively represented as a mixture of chains identical with FS-BA-AT and other chains built up of randomly sulfated alternating 4- and 3-linked α-L-fucopyranose residues.

Advances in Research on Antiviral Activities of Sulfated Polysaccharides from Seaweeds

In recent years, various viral diseases have suddenly erupted, resulting in widespread infection and death. A variety of biological activities from marine natural products have gradually attracted the attention of people. Seaweeds have a wide range of sources, huge output, and high economic benefits. This is very promising in the pharmaceutical industry. In particular, sulfated polysaccharides derived from seaweeds, considered a potential source of bioactive compounds for drug development, have shown antiviral activity against a broad spectrum of viruses, mainly including common DNA viruses and RNA viruses. In addition, sulfated polysaccharides can also improve the body’s immunity. This review focuses on recent advances in antiviral research on the sulfated polysaccharides from seaweeds, including carrageenan, galactan, fucoidan, alginate, ulvan, p-KG03, naviculan, and calcium spirulan. We hope that this review will provide new ideas for the development of COVID-19 therapeutics and vaccines.

Antiviral Polymers: A Review

Polymers, due to their high molecular weight, tunable architecture, functionality, and buffering effect for endosomal escape, possess unique properties as a carrier or prophylactic agent in preventing pandemic outbreak of new viruses. Polymers are used as a carrier to reduce the minimum required dose, bioavailability, and therapeutic effectiveness of antiviral agents. Polymers are also used as multifunctional nanomaterials to, directly or indirectly, inhibit viral infections. Multifunctional polymers can interact directly with envelope glycoproteins on the viral surface to block fusion and entry of the virus in the host cell. Polymers can indirectly mobilize the immune system by activating macrophages and natural killer cells against the invading virus. This review covers natural and synthetic polymers that possess antiviral activity, their mechanism of action, and the effect of material properties like chemical composition, molecular weight, functional groups, and charge density on antiviral activity. Natural polymers like carrageenan, chitosan, fucoidan, and phosphorothioate oligonucleotides, and synthetic polymers like dendrimers and sialylated polymers are reviewed. This review discusses the steps in the viral replication cycle from binding to cell surface receptors to viral-cell fusion, replication, assembly, and release of the virus from the host cell that antiviral polymers interfere with to block viral infections.

Polysaccharides from Platycodonis Radix ameliorated respiratory syncytial virus-induced epithelial cell apoptosis and inflammation through activation of miR-181a-mediated Hippo and SIRT1 pathways

Respiratory syncytial virus (RSV) is the leading cause of bronchiolitis in young children, but there are few safe and effective treatments for this disease. Platycodonis Radix is widely used as an antitussive and expectorant drug for preventing various diseases in lower respiratory tract, in which the polysaccharides are one of the main bioactivity constituents. In this study, the protective effects of the P. Radix polysaccharides (PRP) against RSV-induced bronchiolitis in juvenile mice and RSV-induced apoptosis of epithelial HEp-2 cells were investigated. The results showed that PRP obviously decreased the levels of IL-1β, IL-4, IL-6, TNF-α, IFN-γ and TSLP in lung tissues, and reduced the number of inflammatory cells in bronchoalveolar lavage fluid (BALF) of RSV-infected mice. Furthermore, it reduced the apoptosis of RSV-infected HEp-2 cells and remarkably inhibited the mRNA expressions of RSV L gene, which indicated that PRP affected transcription and replication of RSV in host cells. Compared with that in RSV-infected group, miR-181a-5p in the PRP-treated group presented the highest relative abundance and its expression was violently reduced by approximately 30%. Mechanistically, PRP had the similar effects as miR-181a-5p antagomir on RSV-induced apoptosis and inflammation in HEp-2 cells via upregulating BCL2, MLL3 and SIRT1, which could be reversed by miR-181a-5p mimic. Therefore, it demonstrated that PRP not only protected against RSV-induced lung inflammation in mice but also inhibited apoptosis of RSV-infected HEp-2 cells via suppressing miR-181a-5p and transcriptionally activating Hippo and SIRT1 pathways.

Antiviral Activities of Algal-Based Sulfated Polysaccharides

An antiviral agent is urgently needed based on the high probability of the emergence and re-emergence of future viral disease, highlighted by the recent global COVID-19 pandemic. The emergence may be seen in the discovery of the Alpha, Beta, Gamma, Delta, and recently discovered Omicron variants of SARS-CoV-2. The need for strategies besides testing and isolation, social distancing, and vaccine development is clear. One of the strategies includes searching for an antiviral agent that provides effective results without toxicity, which is well-presented by significant results for carrageenan nasal spray in providing efficacy against human coronavirus-infected patients. As the primary producer of sulfated polysaccharides, marine plants, including macro- and microalgae, offer versatility in culture, production, and post-isolation development in obtaining the needed antiviral agent. Therefore, this review will describe an attempt to highlight the search for practical and safe antiviral agents from algal-based sulfated polysaccharides and to unveil their features for future development.

Antiviral Activity of Plantago asiatica Polysaccharide against Pseudorabies Virus In Vitro

Pseudorabies (PR) is an acute infectious disease of various domestic animals and wild animals caused by pseudorabies virus (PRV). It is mainly characterized by fever, itching, encephalomyelitis, and respiratory and neurological disorders. Plantago asiatica polysaccharide (PLP), extracted from the whole plant of Plantago asiatica L., showed immunomodulatory and antioxidation effects, but the antiviral activity had not been reported. In this study, the inhibitory effect of PLP on PRV infection was studied. Our study first revealed that PLP could inhibit PRV infection in a dose-dependent manner. By adding PLP at different stages of the virus's life cycle, we revealed that PLP could reduce the attachment and penetration of PRV into PK15 cells. The inhibition of PRV attachment was better than inhibition of PRV penetration. However, PLP did not affect PRV replication and inactivation. In addition, PLP decreased the intracellular ROS levels in infected cells significantly, and ROS scavenger NAC decreased PRV infection. Therefore, our study provided preliminary data of anti-PRV activity of PLP, which was established to be a novel anti-PRV infection agent.

Structure–immunomodulatory activity relationships of dietary polysaccharides

Polysaccharides are usually composed of more than ten monosaccharide units, which are connected by linear or branched glycosidic bonds. The immunomodulatory effect of natural polysaccharides is one of the most important bioactive function. In this review, molecular weight, monosaccharide (including galactose, mannose, rhamnogalacturonan-I arabinogalactan and uronic acid), functional groups (namely sulfate, selenium, and acetyl groups), types of glycoside bond connection (including β-1,3-D-glucosyl, α-1,4-D-glucosyl, β-1,4-D-glucosyl, α-1,6-D-glucosyl, β-1,4-D-mannosyl, and β-1,4-D-Xylopyranosyl), conformation and the branching degrees are systematically identified as their contribution to the immunostimulatory activity of polysaccharides. At present, studies on the structure-activity relationships of polysaccharides are limited due to their low purity and high heterogeneity. However, it is an important step in providing useful guidance for dietary supplements with polysaccharides. The chemical structures and the process of immune responses induced are necessary to be discussed. Polysaccharides may bind with the cell surface receptors to modulate immune responses. This review mainly discusses the structure-activity relationship of dietary polysaccharides.

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Structure - activity relationships of polysaccharides with immune-enhancing effect are proposed.

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Polysaccharides with the higher molecular weight are helpful to improve immunity.

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Higer galactose, mannose, rhamnogalacturonan-I, arabinogalacta,n and uronic acid contents have immunoregulation.